In recent years, foldable portable telephones have been making progress in multi-functionalization along with being made smaller and thinner. Development is in progress of foldable portable telephones with a hands-free function, which allow communication and message transmission and reception even with the both cabinets closed and placed on a desk (see, for example, JP 2003-18257, A, JP 2003-51871, A and JP 2003-134201, A).
A foldable portable telephone shown in for example FIG. 17 and FIG. 18 has been proposed as a foldable portable telephone having a hands-free function.
The foldable portable telephone includes a body cabinet 8 and a cover cabinet 9 openably/closably coupled to each other through a hinge mechanism 83. A plurality of manual keys 81 and a transmitter 82 are disposed on an inner surface of the body cabinet 8, while a microphone 84 is disposed inside the body cabinet 8 toward the transmitter 82.
The cover cabinet 9 has an inner surface provided with a main display 91 and a first receiver 92 disposed in a position to be opposed to the transmitter 82 with the both cabinets 8, 9 closed. A second receiver 93 is disposed on a rear surface of the cover cabinet 9. The cover cabinet 9 has an interior provided with a first speaker 94 disposed toward the first receiver 92 and a second speaker 95 disposed toward the second receiver 93.
A first projection 85 projects near the transmitter 82 of the body cabinet 8, while a second projection 96 projects near the first receiver 92 of the cover cabinet 9, the both projections 85, 96 being in contact with each other with the both cabinets 8, 9 closed.
With the foldable portable telephone, when the both cabinets 8, 9 are closed as shown in FIG. 18, a cabinet open/close detector (not shown) detects that the both cabinets 8, 9 are closed to feed a detection signal based on the detection to a control circuit (not shown). The control circuit causes the microphone 84 and the second speaker 95 to function in response to the detection signal. Consequently, speech transmission and reception using the microphone 84 and the second speaker 95 become possible in a hands-free condition where the both cabinets 8, 9 are closed and placed on a desk.
However, with the foldable portable telephone, when speech transmission and reception are performed with the both cabinets 8, 9 closed as shown in FIG. 18, vibration of the second speaker 95 can be transmitted to the first speaker 94 through the air inside the cover cabinet 9 to thereby vibrate the first speaker 94. This can cause the first speaker 94 to emit a sound wave having a waveform approximated to that of a sound wave emitted from the second speaker 95. The sound wave emitted from the first speaker 94 can be transmitted to the microphone 84 because the first speaker 94 is opposed to the microphone 84 through the first receiver 92 and the transmitter 82. Consequently, a loop of an acoustic transmission path can be formed between the second speaker 95 and the microphone 84 through the first speaker 94. This can transmit the other party's voice emitted from the second speaker 95 to the microphone 84 to generate a phenomenon where the voice is transmitted to the other party, i.e., howling, which has been causing a problem of giving the other party displeasure.
Accordingly, an object of the present invention is to prevent or suppress a howling phenomenon in a foldable portable terminal with a hands-free function including an openably/closably coupled pair of cabinets.